On 02/12/13 02:54 PM, Zardosht Kasheff wrote:
> Hello all,
>
> In MySQL and/or MariaDB, are there any hooks or methods one can use to
> learn why a query plan is chosen over alternatives? We sometimes
> notice that a different query plan is chosen for us than InnoDB (which
> may be fine, given we are a different storage engine), and we would
> like to better understand why. Is there any debug parameter that gets
> MySQL to output decisions made in the optimizer?
MySQL 5.6 has optimizer tracing which outputs the decisions made by the
optimizer. See http://dev.mysql.com/doc/internals/en/optimizer-tracing.html
Hope this helps,
--
Øystein
